package security.crypto.aes;

/*
 *****************************************************************************
 *                                                                           *
 *                      10101000100010001010101100101010101                  *
 *                      0101010101               0101010100                  *
 *                      0101010101               0101010100                  *
 *                      1010101010        10101  0101110101                  *
 *                      1010101010       01  10  0101011101                  *
 *                      1010111010       01      0101010101                  *
 *                       010101010  01  010 0101 010101010                   *
 *                       010101010  01  010  01  010101011                   *
 *                        01010101  01  010  01  01010101                    *
 *                        11010101  01  010  01  01010110                    *
 *                         1010101  01  010  01  0101000                     *
 *                         1110101  01  010  01  0101001                     *
 *                          110101      010      010001                      *
 *                           10101     001       01011                       *
 *                            1101  10101        0101                        *
 *                             110               011                         *
 *                              10               01                          *
 *                               01             10                           *
 *                                 00         10                             *
 *                                  01       01                              *
 *                                    01   01                                *
 *                                      010                                  *
 *                                       1                                   *
 *                                                                           *
 *                        Universidade T�cnica de Lisboa                     *
 *                                                                           *
 *                          Instituto Superior T�cnico                       *
 *                                                                           *
 *                                                                           *
 *                                                                           *
 *     								   AIAC                                  *
 *     		Aplica��es e Implementa��es de Algoritmos Criptogr�ficos         *
 *                                											 *
 *                                AES application                            *
 *                                                                           *
 *                       	 Professor Ricardo Chaves          	             *
 *                                                                           *
 *                                                                           *
 *****************************************************************************
 * @filename: AES.java                                                       *
 * @language: Java                                                           *
 * @last update at: 2010-04-13                                               *
 *****************************************************************************
 * @students that colaborated on this file:                                  *
 *  55962 - Manuel Monterroso - m.monterroso@gmail.com			             *
 *  57441 - Ant�nio Lages - antoniomslages@ist.utl.pt                        *
 *****************************************************************************
 */

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;


/*
 *****************************************************************************
 *       Advanced Encryption Standard implementation in JAVA.   			 *
 *      																	 *
 *       Solution based on Niyaz PK's implementation in C.      			 *
 *		 All credits reserved.												 * 
 *																			 *
 *****************************************************************************
 *   This is an application to encrypt and decrypt binary files using 		 *
 *   AES algorithm. AES algorithm is also called Rijndael algorithm. 		 *
 *   It is recommended for non-classified by the National Institute of 		 *
 *   Standards and Technology(NIST), USA. Now-a-days AES is being used 		 *
 *   for almost all encryption applications all around the world.			 *
 *****************************************************************************
 */
public class AES {
	
	private boolean Cipher = false; 				// Cipher operation: encryption (false) or decryption (true)
	private int CMode = 0;						// Block cipher mode: ECB (0) / CBC (1) / CTR (2)
	private byte[] RoundKey = new byte[240];		// The array that stores the round keys.
	private int keyBits = 128;					// By omission, keyBits = 128
	
	// The number of columns comprising a state in AES. This is a constant in AES. Value=4
	private final int Nb=4;	
	// The number of rounds in AES Cipher. It is simply initiated to zero. The actual value is received in the program.
	private int Nr=10;
	// The number of 32 bit words in the key. It is simply initiated to zero. The actual value is received in the program.
	private int Nk=4;
	
	private final int[] rsbox = { 
		0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
		0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
		0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
		0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
		0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
		0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
		0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
		0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
		0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
		0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
		0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
		0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
		0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
		0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
		0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
		0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d };
	

	private final int[] sbox = {
		//0     1    2      3     4    5     6     7      8     9     A      B     C     D     E     F
		0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, //0
		0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, //1
		0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, //2
		0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, //3
		0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, //4
		0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, //5
		0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, //6
		0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, //7
		0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, //8
		0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, //9
		0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, //A
		0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, //B
		0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, //C
		0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, //D
		0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, //E
		0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16}; //F
	
	
	// The round constant word array, Rcon[i], contains the values given by x to the e power (i-1) being powers of x 
	// (x is denoted as {02}) in the field GF(28). Note that i starts at 1, not 0).
	private final char[] Rcon = {
		0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 
		0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 
		0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 
		0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 
		0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 
		0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 
		0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 
		0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 
		0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 
		0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 
		0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 
		0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 
		0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 
		0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 
		0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 
		0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb  };
	
	private AES_encrypt _aesEncrypt;
	private AES_decrypt _aesDecrypt;

	//*****************************************************************************************************************
	// This method performs the required initializations, which includes the key expansion
	public void init (boolean ciphered, int cmode, byte[] key) {
		
		Cipher = ciphered;
		setCMode(cmode);
		
		keyExpansion(key);
		
		_aesEncrypt = new AES_encrypt();
		_aesEncrypt.init(this);
		
		if(Cipher){
			_aesDecrypt = new AES_decrypt();
			_aesDecrypt.init(this, _aesEncrypt);
		}		
		
	}
	
	// This method performs the ciphering of the input data, using the parameters specified in the init method.
	// Note: If the last bytes of the input data do not form a full block, the bytes are not ciphered at that instance.
	public byte[] update (byte[] bytes) {
		
		byte[] tmp;
		
		if(Cipher)
			tmp = _aesDecrypt.update(bytes);
		else 
			tmp = _aesEncrypt.update(bytes);
		
		return tmp;
	}

	// This method performs the ciphering of the input data, using the parameters specified in the init method.
	// Note: If the last bytes of the input data do not form a full block, the bytes are not ciphered at that instance.
	public byte[] update (byte[] bytes, int inputlen) {
		
		byte[] tmp;
		
		if(Cipher)
			tmp = _aesDecrypt.update(bytes, inputlen);
		else 
			tmp = _aesEncrypt.update(bytes, inputlen);
		
		return tmp;
	}
	
	// This method performs the ciphering of the input data, using the parameters specified in the init
	// method. This method also performs the necessary procedures to conclude the ciphering of the
	// data stream, including the addition of necessary padding.
	public byte[] doFinal (byte[] bytes) {
		
		byte[] tmp;
		
		if(Cipher)
			tmp = _aesDecrypt.doFinal(bytes);
		else 
			tmp = _aesEncrypt.doFinal(bytes);
		
		return tmp;
	}
	
	// This method performs the ciphering of the input data, using the parameters specified in the init
	// method. This method also performs the necessary procedures to conclude the ciphering of the
	// data stream, including the addition of necessary padding.	
	public byte[] doFinal (byte[] bytes, int inputlen) {
		
		byte[] tmp;
		
		if(Cipher)
			tmp = _aesDecrypt.doFinal(bytes, inputlen);
		else 
			tmp = _aesEncrypt.doFinal(bytes, inputlen);
		
		return tmp;
	}

	//*****************************************************************************************************************
	// This function produces Nb(Nr+1) round keys. The round keys are used in each round to encrypt or decrypt the states
	private void keyExpansion(byte[] key) {

		int i, j;
		byte k;

		// The first round key is the key itself.
		for (i = 0; i < Nk; i++) {

			RoundKey[i * 4] = key[i * 4];
			RoundKey[i * 4 + 1] = key[i * 4 + 1];
			RoundKey[i * 4 + 2] = key[i * 4 + 2];
			RoundKey[i * 4 + 3] = key[i * 4 + 3];
		}

		// All other round keys are found from the previous round keys.
		while (i < (Nb * (Nr + 1))) {

			byte[] temp = new byte[4];

			for (j = 0; j < 4; j++) {

				temp[j] = RoundKey[((i - 1) * 4 + j)];
			}

			if ((i % Nk) == 0) {
				
				// RotWord() is a function that rotates the 4 bytes in a word to the left once.
				// [a0,a1,a2,a3] becomes [a1,a2,a3,a0]

				// Function RotWord()
				k = temp[0];
				temp[0] = temp[1];
				temp[1] = temp[2];
				temp[2] = temp[3];
				temp[3] = k;

				// SubWord() is a function that takes a four-byte input word and applies the S-box
				// to each of the four bytes to produce an output word.

				// Function Subword()
				temp[0] = (byte) getSBoxValue((int) temp[0]);
				temp[1] = (byte) getSBoxValue((int) temp[1]);
				temp[2] = (byte) getSBoxValue((int) temp[2]);
				temp[3] = (byte) getSBoxValue((int) temp[3]);
				
				temp[0] = (byte) ((temp[0]) ^ (byte) (Rcon[i / Nk]));

			} else

			if (Nk > 6 && ((i % Nk) == 4)) {

				// Function Subword()
				temp[0] = (byte) getSBoxValue((int) temp[0]);
				temp[1] = (byte) getSBoxValue((int) temp[1]);
				temp[2] = (byte) getSBoxValue((int) temp[2]);
				temp[3] = (byte) getSBoxValue((int) temp[3]);

			}

			RoundKey[i * 4 + 0] = (byte) (RoundKey[(i - Nk) * 4 + 0] ^ temp[0]);
			RoundKey[i * 4 + 1] = (byte) (RoundKey[(i - Nk) * 4 + 1] ^ temp[1]);
			RoundKey[i * 4 + 2] = (byte) (RoundKey[(i - Nk) * 4 + 2] ^ temp[2]);
			RoundKey[i * 4 + 3] = (byte) (RoundKey[(i - Nk) * 4 + 3] ^ temp[3]);

			i++;
		}
	}
		
	int getSBoxValue(int num){
		
		if (num >= 0)
			return sbox[num];
		else return sbox[256+num];
	}
	
	int getSBoxInvertValue(int num){
		
		if (num >= 0)
			return rsbox[num];
		else return rsbox[256+num];
	}
	
	private void usage () {
		
		System.out.println("***Please restart the application with the following command-line configuration:***\n" +
		   				   "java AES [-e/d] [�cbc/ecb/ctr] [-128/156/192] [-f Keyfile] [-k Key] -i inputfile [-o outputfile]");
		System.exit(-1);
	}
	
	int getNb() {	
		return Nb;
	}

	int getNr() {	
		return Nr;
	}

	void setRoundKey(byte[] roundKey) {
		RoundKey = roundKey;
	}

	byte[] getRoundKey() {

		return RoundKey;
	}

	private void setCMode(int cMode) {
		CMode = cMode;
	}

	int getCMode() {
		return CMode;
	}
	//*****************************************************************************************************************
	public static void main(String[] args) {
		AES aes = new AES();
		
		boolean cipher = false;
		int cmode = 0;

		int tmp = 0;
		boolean isKeySet = false;
		int length = args.length;
		
		// key - it is the array that holds the key for encryption.
		byte[] key = new byte[16];
		// input - it is the array that holds the input to be encrypted/ decrypted
		byte[] input = new byte[2048];
		// output - it is the array that holds the output that was encrypted/ decrypted and will be written to a file
		byte[] output = null;
		
		if (length < 5 || length > 11)	aes.usage();
		
		if (args[tmp].compareTo("-e") == 0)
			tmp++;
		else
			if (args[tmp].equals("-d")) {
				tmp++;
				cipher = true;
			}
		
		if (args[tmp].equals("-ecb"))
			tmp++;
		else
			if (args[tmp].equals("-cbc")) {
				tmp++;
				cmode = 1;
			} else 
				if (args[tmp].equals("-ctr")) {
					tmp++;
					cmode = 2;
				}
		
		if (args[tmp].equals("-128")) {
			tmp++;
			key = new byte[16];
		} else 
			if (args[tmp].equals("-192")) {
				tmp++;
				aes.keyBits = 192;
				key = new byte[24];
			} else
				if (args[tmp].equals("-256")) {
					tmp++;
					aes.keyBits = 256;	
					key = new byte[32];
				}
		
		aes.Nk = aes.keyBits / 32;
		aes.Nr = aes.Nk + 6;
		
		if (args[tmp].equals("-f")) {
			tmp++;
			String keyFileDirectory = args[tmp];
			tmp++;
			isKeySet = true;
			
			try{
				
				InputStream fis = new FileInputStream(keyFileDirectory);
				BufferedInputStream bis = new BufferedInputStream(fis);
				
			    int offset = 0;
		        int numRead = 0;
		        
		        // Reads the bytes to the key array
		        while ( (offset < key.length)
		                &&
		                ( (numRead = bis.read(key, offset, key.length-offset)) >= 0) ) {
		            offset += numRead;
		        }
		        
		        // Ensure that the key file hasn't more bytes than expected
		        if (bis.available() > 0) {
		            throw new IOException("Could not completely read the key file because it was bigger than expected!");
		        }
			 
			    bis.close();
			    fis.close();
			    
			} catch (FileNotFoundException ex) {
				System.err.println(ex);
		    } catch (IOException ex) {
		    	System.err.println(ex);
		    } 
		}
		
		if (length - tmp == 0) {
			System.out.println("You must set the directory of the file you want to cipher!\n" +
							   "***********************************************************************************");
			aes.usage();
		}
		
		if (args[tmp].equals("-k") && isKeySet == false) {
			tmp++;
			String consoleKey = args[tmp];
			key = new byte[consoleKey.length()];
			key = consoleKey.getBytes();
			tmp++;
			isKeySet = true;
		} else 
			if (args[tmp].equals("-k") && isKeySet == true) {
				System.out.println("You've already set the file key to cipher the file!\n" +
				   				   "***********************************************************************************");
				aes.usage();
			}
		
		if (length - tmp == 0) {
			System.out.println("You must set the directory of the file you want to cipher!\n" +
							   "***********************************************************************************");
			aes.usage();            
		}
		
		if (isKeySet == false) {
			System.out.println("You must set a key to cipher the file!\n" +
							   "***********************************************************************************");
			System.out.println("OLA!");aes.usage();
		}
		
		String inputFileDirectory = null;
		String outputFileDirectory = "output";
		
		if (args[tmp].equals("-i")) {
			tmp++;
			
			if (length - tmp == 0) {
				System.out.println("You must set the directory of the file you want to cipher!\n" +
								   "***********************************************************************************");
				aes.usage();
				
			}
			
			inputFileDirectory = args[tmp];
			
			tmp++;
			
		} else {
			System.out.println("You must set the directory of the file you want to cipher!\n" +
							   "***********************************************************************************");
			aes.usage();
		}
		
		if (length - tmp > 0) {
			
			if (args[tmp].equals("-o")) {
				tmp++;
				if (length - tmp == 0) aes.usage();
				outputFileDirectory = args[tmp];
			}
		}
		
		
		/*************************************************************************************************************/
		aes.init(cipher, cmode, key);
		
		try{
			
			InputStream is = new FileInputStream(inputFileDirectory);
			BufferedInputStream bis = new BufferedInputStream(is);
			OutputStream os = new FileOutputStream(outputFileDirectory);
			BufferedOutputStream bos = new BufferedOutputStream(os);
			
			int inputext_length = input.length;
			
			int globalOffset = 0;
			int currentOffset, numRead;
			
			currentOffset = inputext_length;
			
			while (currentOffset == inputext_length) {
			
				currentOffset = 0;
				numRead = 0;
				
				// Reads the bytes to the input array, 2048 bytes at one time only
				while ( (currentOffset < inputext_length)
						&&
						( (numRead = bis.read(input, currentOffset, inputext_length-currentOffset)) >= 0) ) {
					
					currentOffset += numRead;
					globalOffset += numRead;
				}
				
				output = new byte[currentOffset];
				
				// Ensure all the bytes have been read in and check which function to call and cipher the input 
				if (currentOffset < inputext_length)
					output = aes.doFinal(input, currentOffset);
				else 
					output = aes.update(input);
					
				bos.write(output);
			}
		 
		    bis.close(); bos.close();
		    is.close(); os.close();
		    
		} catch (FileNotFoundException ex) {
			System.err.println(ex);
	    } catch (IOException ex) {
	    	System.err.println(ex);
	    } 
	}
}
